1. Field of the Invention
The present invention relates generally to methods and apparatus for measuring the performance of an optical lens, and more particularly to a model eye system for predicting the in-vivo performance of a vision altering optic, and methods related thereto.
2. Description of Related Art
Numerous descriptions of various eye models are found in the literature. Eye models are helpful for many reasons, including designing contact lenses, modeling vision under various conditions such as refractive surgical procedures, contact lens or spectacle wear, and near vision, for biometric applications, and many others.
It has long been a challenge in the field of vision correction to be able to predict the subjective response of a patient prior to actually altering the patient""s vision, either surgically or by external means such as spectacles or contact lenses, for example. Moreover, soft contact lens performance in-vivo, for example, is difficult to predict due to changes in the lens"" surface shapes caused by the actual, variable, corneal contours of people""s eyes, as compared to the manufactured shape of the lens. Thus, the ability to accurately predict the in-vivo performance of a vision altering optic has many obvious advantages like reducing the time, cost, and uncertainty involved in efforts to improve people""s vision. Accordingly, the recognition of the problems and advantages of predicting performance of a visual alteration has lead to the instant invention which is described in greater detail below.
The invention pertains to a model eye system useable in combination with a variety of vision altering optics such as contact lenses, IOLs, spectacle lenses, representative crystalline lenses, inlays, onlays, and others to remotely predict the in-vivo performance of the vision altering optic, and methods relating thereto. The term xe2x80x9cremotelyxe2x80x9d herein refers to not being in-vivo, e.g., measuring a contact lens performance on a model eye to predict its performance when being worn on a real eye.
A model eye system according to an embodiment of the invention includes a structural housing; a representative cornea having an anterior surface and a posterior surface; a retinal surface located posterior to the posterior surface of the cornea; and a dispersion medium occupying the space between the cornea and the retinal surface (more specifically between the posterior corneal surface and the retinal surface). In an aspect of this embodiment, an enclosure provides a controlled environment around the anterior corneal surface and a vision altering optic under measurement if such an optic is present. The model eye system may have one or more clear apertures, variable apertures, and/or pupils positioned for light entry and exit or pupil function replication. The representative cornea is anatomically transparent. At least part of the anterior corneal surface has a shape to replicate anatomical function, while a specific shape imparted to the anterior corneal surface is preferably selected to alleviate and/or replicate lens fitting problems and more accurately predict in-vivo lens performance. At least part of the posterior surface of the representative cornea is also shaped; however, the posterior corneal shape preferably provides the model eye with optical power and with selected higher-order aberration content characteristic of an actual eye. A representative retinal surface forms the back surface of the eye model system and can be optically or physically transmissive, diffusely or specularly reflective, or customized as to material, construction and/or shape to have the desired characteristics for the investigation being conducted; for example, it or any other component of the model eye system may be tilted and/or decentered. A light source can thus be positioned in front of or behind the model eye system as desired. The space between the posterior corneal surface and the retinal surface is occupied by a dispersion medium that models the chromatic dispersion characteristics of an actual eye. The separation distance between the retinal surface and the posterior corneal surface is made variable via flexible model eye housing joints, for example, in order to provide a selected amount of defocus in the eye model.
According to another embodiment of the invention, a method for remotely measuring the performance of a vision altering optic to predict its performance in-vivo includes the steps of obtaining a value of a pre-selected metric of a model eye; appropriately locating the optic to be measured with respect to the model eye; and obtaining a value of the pre-selected metric for the optic and model eye combination. Various metrics for the model eye and the optic/model eye combination are envisioned by the invention and include, but are not limited to, topography measurements, wavefront measurements, modulation transfer function (MTF) measurements, point spread function (PSF) measurements, interferometry measurements, and physical and optical parameters and characteristics of the eye model and/or optic/eye model combination. Testing methods may include various modes and/or types of illumination, adjustment of eye model components to simulate anatomical conditions, and other adaptations appreciated by a person skilled in the art.
The explicit and implicit objects and advantages of the invention will now be described in more detail with reference to the drawing figures listed below, the detailed description of the preferred embodiments, and the appended claims.